Abstract
Contamination on printed circuit boards prevented two automatic typesetters from properly performing their design function in a Midwestern newspaper office. An investigation was conducted with the objective of determining:
The contaminant composition
A mechanism for the problem
A method of cleaning the boards
A method to prevent recurrence
Two representative boards were taken from one of the units to use in the investigation. The condition of the boards was photographically documented. Two types of contaminants were found on the boards. One type of contamination was a blue-green powder found on copper surfaces; its composition was determined to be primarily copper (II) hydroxide. A gray-black contamination which was identified as most probably being tin (IV) oxide, was found on the tin-lead foils. It was determined that these were the only two of 185 units of that model which had such a problem. Also, they were the only ones in the same room with photographic processors. Air inside these units was found to contain vapors from the developing solution used in the processors. The developing station was primarily an aqueous potassium hydroxide solution.
The contamination was found to corrosion products formed by developing solution vapors entering the typesetters due to their sharing common openings with photographic processors. Exhausting these vapors from the processor outside the composing room prevented the return of the problem.
